package com.aggregate.pay.linkpay.support.utils;

import java.io.ByteArrayOutputStream;
import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.Signature;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

import javax.crypto.Cipher;

/**
 * 
 * @author Moyq5
 * @date 2017年4月25日
 */
public class RSA {

	/**  
     * 加密算法RSA  
     */  
    public static final String KEY_ALGORITHM = "RSA";  
  
    /**  
     * 签名算法  
     */  
    public static final String SIGNATURE_ALGORITHM = "MD5withRSA";  
  
    /**  
     * 获取公钥的key  
     */  
    private static final String PUBLIC_KEY = "RSAPublicKey";  
  
    /**  
     * 获取私钥的key  
     */  
    private static final String PRIVATE_KEY = "RSAPrivateKey";  
  
    /**  
     * RSA最大加密明文大小  
     */  
    private static final int MAX_ENCRYPT_BLOCK = 117;  
  
    /**  
     * RSA最大解密密文大小  
     */  
    private static final int MAX_DECRYPT_BLOCK = 128;  
  
    /**  
     * <p>  
     * 生成密钥对(公钥和私钥)  
     * </p>  
     *   
     * @return  
     * @throws Exception  
     */  
    public static Map<String, Object> genKeyPair() throws Exception {  
        KeyPairGenerator keyPairGen = KeyPairGenerator  
                .getInstance(KEY_ALGORITHM);  
        keyPairGen.initialize(1024);  
        KeyPair keyPair = keyPairGen.generateKeyPair();  
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();  
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();  
        Map<String, Object> keyMap = new HashMap<String, Object>(2);  
        keyMap.put(PUBLIC_KEY, publicKey);  
        keyMap.put(PRIVATE_KEY, privateKey);  
        return keyMap;  
    }  
  
    /**  
     * <p>  
     * 用私钥对信息生成数字签名  
     * </p>  
     *   
     * @param data  
     *            已加密数据  
     * @param privateKey  
     *            私钥(BASE64编码)  
     *   
     * @return  
     * @throws Exception  
     */  
    public static String sign(byte[] data, String privateKey) throws Exception {  
        byte[] keyBytes = Base64.decode(privateKey);  
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);  
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);  
        PrivateKey privateK = keyFactory.generatePrivate(pkcs8KeySpec);  
        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);  
        signature.initSign(privateK);  
        signature.update(data);  
        return Base64.encodeBytes(signature.sign());  
    }  
  
    /**  
     * <p>  
     * 校验数字签名  
     * </p>  
     *   
     * @param data  
     *            已加密数据  
     * @param publicKey  
     *            公钥(BASE64编码)  
     * @param sign  
     *            数字签名  
     *   
     * @return  
     * @throws Exception  
     *   
     */  
    public static boolean verify(byte[] data, String publicKey, String sign)  
            throws Exception {  
        byte[] keyBytes = Base64.decode(publicKey);  
        X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);  
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);  
        PublicKey publicK = keyFactory.generatePublic(keySpec);  
        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);  
        signature.initVerify(publicK);  
        signature.update(data);  
        return signature.verify(Base64.decode(sign));  
    }  
  
    /**  
     * <P>  
     * 私钥解密  
     * </p>  
     *   
     * @param encryptedData  
     *            已加密数据  
     * @param privateKey  
     *            私钥(BASE64编码)  
     * @return  
     * @throws Exception  
     */  
    public static byte[] decryptByPrivateKey(byte[] encryptedData,  
            String privateKey) throws Exception {  
        byte[] keyBytes = Base64.decode(privateKey);  
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);  
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);  
        Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);  
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());  
        cipher.init(Cipher.DECRYPT_MODE, privateK);  
        int inputLen = encryptedData.length;  
        ByteArrayOutputStream out = new ByteArrayOutputStream();  
        int offSet = 0;  
        byte[] cache;  
        int i = 0;  
        // 对数据分段解密  
        while (inputLen - offSet > 0) {  
            if (inputLen - offSet > MAX_DECRYPT_BLOCK) {  
                cache = cipher  
                        .doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);  
            } else {  
                cache = cipher  
                        .doFinal(encryptedData, offSet, inputLen - offSet);  
            }  
            out.write(cache, 0, cache.length);  
            i++;  
            offSet = i * MAX_DECRYPT_BLOCK;  
        }  
        byte[] decryptedData = out.toByteArray();  
        out.close();  
        return decryptedData;  
    }  
  
    /**  
     * <p>  
     * 公钥解密  
     * </p>  
     *   
     * @param encryptedData  
     *            已加密数据  
     * @param publicKey  
     *            公钥(BASE64编码)  
     * @return  
     * @throws Exception  
     */  
    public static byte[] decryptByPublicKey(byte[] encryptedData,  
            String publicKey) throws Exception {  
        byte[] keyBytes = Base64.decode(publicKey);  
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);  
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);  
        Key publicK = keyFactory.generatePublic(x509KeySpec);  
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());  
        cipher.init(Cipher.DECRYPT_MODE, publicK);  
        int inputLen = encryptedData.length;  
        ByteArrayOutputStream out = new ByteArrayOutputStream();  
        int offSet = 0;  
        byte[] cache;  
        int i = 0;  
        // 对数据分段解密  
        while (inputLen - offSet > 0) {  
            if (inputLen - offSet > MAX_DECRYPT_BLOCK) {  
                cache = cipher  
                        .doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);  
            } else {  
                cache = cipher  
                        .doFinal(encryptedData, offSet, inputLen - offSet);  
            }  
            out.write(cache, 0, cache.length);  
            i++;  
            offSet = i * MAX_DECRYPT_BLOCK;  
        }  
        byte[] decryptedData = out.toByteArray();  
        out.close();  
        return decryptedData;  
    }  
  
    /**  
     * <p>  
     * 公钥加密  
     * </p>  
     *   
     * @param data  
     *            源数据  
     * @param publicKey  
     *            公钥(BASE64编码)  
     * @return  
     * @throws Exception  
     */  
    public static byte[] encryptByPublicKey(byte[] data, String publicKey)  
            throws Exception {  
        byte[] keyBytes = Base64.decode(publicKey);  
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);  
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);  
        Key publicK = keyFactory.generatePublic(x509KeySpec);  
        // 对数据加密  
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());  
        cipher.init(Cipher.ENCRYPT_MODE, publicK);  
        int inputLen = data.length;  
        ByteArrayOutputStream out = new ByteArrayOutputStream();  
        int offSet = 0;  
        byte[] cache;  
        int i = 0;  
        // 对数据分段加密  
        while (inputLen - offSet > 0) {  
            if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {  
                cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);  
            } else {  
                cache = cipher.doFinal(data, offSet, inputLen - offSet);  
            }  
            out.write(cache, 0, cache.length);  
            i++;  
            offSet = i * MAX_ENCRYPT_BLOCK;  
        }  
        byte[] encryptedData = out.toByteArray();  
        out.close();  
        return encryptedData;  
    }  
  
    /**  
     * <p>  
     * 私钥加密  
     * </p>  
     *   
     * @param data  
     *            源数据  
     * @param privateKey  
     *            私钥(BASE64编码)  
     * @return  
     * @throws Exception  
     */  
    public static byte[] encryptByPrivateKey(byte[] data, String privateKey)  
            throws Exception {  
        byte[] keyBytes = Base64.decode(privateKey);  
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);  
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);  
        Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);  
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());  
        cipher.init(Cipher.ENCRYPT_MODE, privateK);  
        int inputLen = data.length;  
        ByteArrayOutputStream out = new ByteArrayOutputStream();  
        int offSet = 0;  
        byte[] cache;  
        int i = 0;  
        // 对数据分段加密  
        while (inputLen - offSet > 0) {  
            if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {  
                cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);  
            } else {  
                cache = cipher.doFinal(data, offSet, inputLen - offSet);  
            }  
            out.write(cache, 0, cache.length);  
            i++;  
            offSet = i * MAX_ENCRYPT_BLOCK;  
        }  
        byte[] encryptedData = out.toByteArray();  
        out.close();  
        return encryptedData;  
    }  
  
    /**  
     * <p>  
     * 获取私钥  
     * </p>  
     *   
     * @param keyMap  
     *            密钥对  
     * @return  
     * @throws Exception  
     */  
    public static String getPrivateKey(Map<String, Object> keyMap)  
            throws Exception {  
        Key key = (Key) keyMap.get(PRIVATE_KEY);  
        return Base64.encodeBytes(key.getEncoded());  
    }  
  
    /**  
     * <p>  
     * 获取公钥  
     * </p>  
     *   
     * @param keyMap  
     *            密钥对  
     * @return  
     * @throws Exception  
     */  
    public static String getPublicKey(Map<String, Object> keyMap)  
            throws Exception {  
        Key key = (Key) keyMap.get(PUBLIC_KEY);  
        return Base64.encodeBytes(key.getEncoded());  
    }  
  
}  
